This project attempts to describe the total range of antigens expressed on murine plasmacytomas, to evaluate their ability to induce tumor specific responses under various conditions of immunisation, and to assess which of these antigens are primarily involved in tumor specific immunity in the natural in vivo situation of exposure to a growing tumor. This involves in vitro and in vivo analysis of four general types of antigens, both studies aimed at the purification of the antigen, and the specificity of the resulting immune responses. The areas under investigation concern isolation of C type virus from NZB plasmacytomas; specificity of in vitro T cell immune responses to plasmacytomas under a range of immunising conditions; presence and nature of plasma cell oncofetal antigens; role of immunoglobulin as a tumor antigen; and inhibitory activity of plasma cytomas on the generation of immune responses.